In laser direct-write (LDW) techniques, a laser beam is used to create a patterned surface with spatially-resolved 3D structures by controlled material ablation or deposition. Laser-induced forward transfer (LIFT) is an LDW technique that can be applied in depositing micro-patterns on a surface.
In LIFT, laser photons provide the driving force to catapult a small volume of material from a donor film toward an acceptor substrate. Typically, the laser beam interacts with the inner side of the donor film, which is coated onto a non-absorbing carrier substrate. The incident laser beam, in other words, propagates through the transparent carrier before the photons are absorbed by the inner surface of the film. Above a certain energy threshold, material is ejected from the donor film toward the surface of the substrate, which is generally placed, in LIFT systems that are known in the art, either in close proximity to or even in contact with the donor film. The applied laser energy can be varied in order to control the thrust of forward propulsion that is generated within the irradiated film volume. Nagel and Lippert provide a useful survey of the principles and applications of LIFT in micro-fabrication in “Laser-Induced Forward Transfer for the Fabrication of Devices,” published in Nanomaterials: Processing and Characterization with Lasers, Singh et al., eds. (Wiley-VCH Verlag GmbH & Co. KGaA, 2012), pages 255-316.
LIFT techniques using metal donor films have been developed for a variety of applications, such as repair of electrical circuits. For example, PCT International Publication WO 2010/100635, whose disclosure is incorporated herein by reference, describes a system and method of repairing electrical circuits in which a laser is used to pre-treat a conductor repair area of a conductor formed on a circuit substrate. The laser beam is applied to a donor substrate in a manner that causes a portion of the donor substrate to be detached therefrom and to be transferred to a predetermined conductor location.
As another example, PCT International Publication WO 2015/056253 (published after the priority date of the present patent application), whose disclosure is incorporated herein by reference, describes a method for material deposition in which a transparent donor substrate has opposing first and second surfaces and multiple donor films including different, respective materials on the second surface. The donor substrate is positioned in proximity to an acceptor substrate, with the second surface facing toward the acceptor substrate. Pulses of laser radiation are directed to pass through the first surface of the donor substrate and impinge on the donor films so as to induce ejection of molten droplets containing a bulk mixture of the different materials from the donor films onto the acceptor substrate. Further details of this sort of LIFT technique are described in PCT International Publication WO 2015/181810 (also published after the priority date of the present patent application), whose disclosure is likewise incorporated herein by reference.
Some 3D fabrication techniques use sacrificial supports in creating a desired structure. For example, U.S. Patent Application Publication 2015/0197862 describes an additive metal deposition process in which a build piece is made from a build plan created from a three-dimensional definition of a desired part. The build plan has a first set of dimensions corresponding to the desired part and includes a support structure. The build piece is to a chemical etchant such that the support structure is removed from the build piece and the dimensions of the build piece corresponding to the desired part are reduced to a second set of dimensions.